Blender Operation Success or Failure Feedback?
F6 (operator properties)

Operators may still be active, if you press F6 after noticing a seemingly 'no-op' operator you can get a chance to tweak parameters.



Info Panel (Operator reporting)

As a rule you will get some kind of confirmation that an operator has completed, you could drop down the Info panel to see any output printed by the operator.



Terminal / Console

For more verbose messages sometimes operators print to the Command window, on windows this can be opened while Blender is running ( Window > Toggle System Console). On osx or linux Blender needs to be started from a terminal to get the print-outs.

Windows users be warned
Don't close the Console window manually using the X, that will close Blender. To close the System Console, click the menu item at Window > Toggle System Console again -- that will toggle the console off.